I have an 02 Z71 5.3L. No towing or plowing, almost all highway. At 36,000 sun shell gear went. Dealer fixed, work order said with re-engineered part.
Now I have 57,000 and when shifting from 1st to 2nd there is occasionally, what I would call, a slight shutter or slip. This only occurs when fully warmed up. No service lights.
The TSB #020730030(A) I found seems to describe this condition along with "Install generator voltage sense circuit".
The service advisor here knows nothing about. He said bring it in and give it to the trans guy. 3 trans shops never heard of it. Thats encouraging.
Can anyone tell me what is involved here or what I am headed for? Stop driving?

ConditionSome customers may comment that the transmission slips, a shudder, chuggle, or vibration is felt when the transmission shifts from first to second gear.

CauseA 12 Hz electrical feedback from the charging circuit may be affecting the transmission pressure control solenoid, causing a fluctuation of the line pressure within the transmission.

Diagnostic TipRoad test the vehicle under the following conditions:

• Throttle position is less than 15 percent.

• Engine coolant and transmission fluid are at full operating temperature.

• The outside ambient temperature is warmer than 24°C (75°F).

If the condition is present, disconnect the generator 4 cavity connector (2 wires in the connector) and retest.

If the condition is no longer present, perform the correction listed below.

If the condition remains unchanged, the condition will not be corrected with this procedure. Look for other causes of the condition.

CorrectionInstall an external sense lead to the generator assembly. This is accomplished by adding a wire from the generator four wire connector to the generator output BAT terminal.

Disconnect the negative battery cable from the battery/batteries. Slide the protective boot on the generator BAT terminal aside and remove the retainer and wire cable from the BAT terminal. Unplug the generator 4-cavity terminal from the top of the generator. Inspect cavity D on the generator connector for a red cavity plug. • If a red cavity plug is present, it is not necessary to replace the generator connector. Remove the CPA and save. Remove the red cavity plug and continue with step 9.

• If a red cavity plug is NOT present, continue with the next step.

Remove and save the orange weatherpack seal and CPA from the 4-way connector. Using the proper terminal removal tool, remove the two or three wires from the 4-way connector. • On vehicles without Supplemental Brake Assist (SBA), install a red cavity plug, P/N 12059168, into cavity "A" of the new 4-way connector, P/N 12186568.

• On some 2003 model year vehicles with SBA, install the dark blue (Circuit 5668) wire of the vehicle wiring harness into cavity "A" of the new 4-way connector.

Install the brown (Circuit 25) wire of the vehicle wiring harness into cavity "B" of the new 4-way connector. Install the gray (Circuit 23) wire of the vehicle wiring harness into cavity "C" of the new 4-way connector. Obtain a piece of 0.80 mm/18GA black wire, 254 mm (8 in) long. Install a red terminal seal, P/N 12048086, and terminal, P/N 12048074, (crimp and solder) on one end of the new black wire. Install the new black wire into cavity "D" of the new 4-way connector. Reinstall the connector seal and CPA, from the original connector, to the new connector. Plug the 4-way connector into the generator. Route the black wire to the generator BAT terminal, sliding the wire into the small end to the output terminal boot, along side the generator output wire. Crimp and solder the ring terminal, P/N 12103514, on the open end of the new black wire. Place the generator output wire and the new black wire onto the generator BAT terminal and install the retainer. Tighten Tighten to the BAT terminal retainer to 9 N·m (80 lb in).

Part numbers shown above which have an (*) are found in the terminal repair kit, J 38125. They may be ordered either from GMSPO or SPX Kent Moore.

Parts are currently available from GMSPO.

Warranty InformationFor vehicles repaired under warranty, use:

Labor Operation Description Labor Time

*N8505 Rewire Generator, 1-2 shudder 0.7 hr

*This is a unique labor operation number for use only with this bulletin. This number will not be published in the Labor Time Guide.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

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I am feelin better. The diagnostic tips are right on.
When I was in N. WI and not driving much, no problem. Headed to Florida last week, got off the highway in Ga and said "what the ---- was that" ?
Made it to Bonita Springs next day, same problem. Cold fluids, no problems.
Started doing searches and found the TSB. Didnt want to pay for a new trans if I dont need it. I'll be hear till FEB and didnt know who to trust. Tomorrow I'll be under the hood or checking referrals for a shop.
Thanks for your fast reply.

I had this same problem with an '03 Silverado w/ 5.3 and 4L60E and did the alternator circuit fix, but the problem is still there. Most noticable with hot fluid low to medium acceleration, but basically does it all the time. Do you know of any other causes that could lead to this?? I recalled possibly seeing a tsb to replace the pressure control solenoid...is that legit?

Also, is this 'slippage' doing possible damage? It's been doing it for awhile, it shifts...then 'slips' a little...then you feel it engage. I changed the trans filter a couple weeks ago, and there was more material than I'd like to see...but not necessarily abnormal. Any help is much appreciated.

I had this same problem with an '03 Silverado w/ 5.3 and 4L60E and did the alternator circuit fix, but the problem is still there. Most noticable with hot fluid low to medium acceleration, but basically does it all the time. Do you know of any other causes that could lead to this?? I recalled possibly seeing a tsb to replace the pressure control solenoid...is that legit?

Also, is this 'slippage' doing possible damage? It's been doing it for awhile, it shifts...then 'slips' a little...then you feel it engage. I changed the trans filter a couple weeks ago, and there was more material than I'd like to see...but not necessarily abnormal. Any help is much appreciated.

I'm sorry, I'm not really a tranny guy. Last time I worked on a trans it was a 350 or 400. That's many, many years ago and transmissions were purely mechanical. They've changed immensely since that time. I know what little bit I know through osmosis. If it's a common problem or a TSB I've seen, I can sometimes help, but otherwise I'm not the guy to go to.